How to create dynamic clouds?
First of all go here and read this answer: How to use Blender's dynamic sky add-on?

Go to Node Editor and switch to World mode.

In paragraph Night sky with stars (from the linked answer) you can see whole node setup for Dynamic Sky add-on. Find part Clouds/Stars and Texture Mapping node there:



Now you can animate any of the Location values to get clouds moving in chosen direction.